# Science- Physics Forces And Their Effects

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Resultant Forces

• When an object is stationary or moving at constant velocity then there is zero resultant force on the object. This means that all opposing forces are equal toeach other & cancel each other out
• There may be several forces acting on an object in different directions, these forces can have different strengths and directions
• If the forces are acting in the same direction they can be added together resulting in a larger resultant force and acts like a single force on the object e.g. if there was a 10N force and a 5N force pointing in the same direction then the resultant force would be 15N.
• Body Force diagrams- Length of arrows represent the size of the force on the object. If the top arrow is bigger than the bottom then the acceleration is upwards. If the arrows are balanced then that means that the resultant force is 0.
• Momentum of a moving object= mass x velocity
• Momentum can be increased by either increasing mass or velocity
• Resultant force causes a body to accelerate which means that there would be a change in velocity. This means that a resultant force would cause a change in momentum.

Friction & Heat

• Friction is the force that opposes one surface moving over another e.g. An object placed on a sloped surface should slide down, it not sliding down means that there is friction between the object and the slope that's stopping the object from moving.
• Friction can be a help as we wouldn't be able to walk if there was no friction between shoe soles and the ground because our feet would just slip backwards if we tried to walk. There needs to be friction between roads and tyres in order

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